1. Environmental control of metabolism
Key Area 2.6
Environmental control of metabolism
Growth media and environmental factors
Phases of growth
Control of metabolism

2. Word Splat! Cyclic fluctuation Migration Daily Torpor Extremophile
Predictive
Transmitter
Dormancy
Hibernation
Innate
Learned
Aestivation
Consequential

3. Growth of Micro-organisms
Learning Intentions
What do microorganisms require for synthesis?
What are the requirements for culture of microorganisms?

4. Microorganisms This is a very brooooooooad term
Some are prokaryotes e.g. E.coli
Some are archaea e.g. thermophiles
Some are eukaryotes e.g. Yeast and penicillium
They all have different requirements for growth 4

5. Why use microorganisms?
Easy to culture
Reproduce and grow quickly
Their food source is usually cheap
Make useful products
Their metabolism can be manipulated 5

6. Growing microorganisms
What are the requirements for growth of a microorganism?
Temperature pH
Gaseous environment
Light? 6

7. Growth medium Liquid medium – broth Solid medium – agar
Growth medium is contained in Petri dishes, flasks, bottles or large stainless steel fermenters, and is given the ingredients that an organism requires. 7

8. Chemicals in growth medium
The growth of the micro-organism is directly affected by the chemical components of its growth medium
Some use simple chemical substrates, others require more complex compounds such as vitamins or fatty acids
It uses chemicals for biosynthesis – building biological molecules 8

10. Chemicals in growth medium
Chemical requirement
Source of chemical
Explanation
Carbon
Carbohydrate
Provide energy and raw materials for biosynthesis
Hydrogen
Water + organic compounds
Essential component of organic materials
Oxygen
Water and air
component of organic materials and final H+ acceptor in aerobic respiration
Nitrogen
Compounds with ammonium/nitrate group
Needed for synthesis of nucleic acids, amino acids and proteins
Phorphorus
Compound with phosphate group
Needed for synthesis of nucleic acids and ATP
Sulphur
Compound with sulphate group
Needed for synthesis of some amino acids 10

11. Aseptic technique Why do we use aseptic technique?
To prevent contamination of the microbe we are growing.
To prevent the organism we are culturing contaminating the environment.
Identify 5 methods of aseptic technique 11

12. Computer controlled fermenter
Used to provide aseptic conditions
Fermenters grow
micro-organisms on a vast
scale to produce useful
products e.g. Antibiotics
These hold thousands of
litres of nutrient liquid 12

13. Computer controlled fermenter
Sensors detect environmental conditions
If these vary from the optimum the computer responds by adjusting the required temperature/pH/O₂ or glucose concentration 13

14. Why do you think computer controlled fermenters are effective?
Product monitoring
When conditions are appropriate the required product is released from the micro-organism into the surrounding medium
When the necessary volume/concentration of product has been produces computer controlled technology halts the process
Why do you think computer controlled fermenters are effective?
Saves energy + prevents raw materials being wasted 14

15. Starter: 5,4,3,2,1!
What 5 different elements are required for the growth of an organism?
Identify 4 procedures to ensure aseptic technique.
Name 3 factors that would have to be controlled in a fermenter.
Name 2 different types of growth medium.
Name 1 type of micro-organism

16. Patterns of Growth Learning Intentions
What shape does the growth pattern graph of a microorganism take?

17. Growth
Growth occurs when the synthesis of organic materials by an organism exceeds the rate of their breakdown.
Growth is an irreversible increase of dry biomass
Why is dry biomass a more reliable measurement of growth than fresh biomass? 17

18. Fresh mass

19. Measuring micro-organisms
Measuring dry biomass of micro-organisms is not practical
Why?
Growth of micro-organisms involves measuring an increase in cell number over a period of time 19

20. Generation time
Time taken for a cell to divide is generation time or doubling time
Organisms growing in liquid medium use nutrients and secrete metabolites back into the medium
These changes cause the pattern of growth to vary over time 20

21. log/exponential phase Stationary phase death phase
Lag phase
log/exponential phase
Stationary phase
death phase
(cells cm-³)(logarithmic scale)
Number of micro-organisms
time

22. In the lag phase there is little or no increase in cell number
Cells adjust to the growth medium
They may induce enzymes to begin metabolism
(cells cm-³)(logarithmic scale)
Number of micro-organisms
time
Lag phase

23. Cells grow and multiply at maximum rate
Cell number becomes so large that it becomes difficult to plot points accurately
(cells cm-³)(logarithmic scale)
Number of micro-organisms
time
log/exponential phase

24. This is sometimes because metabolites can be toxic
As nutrients in medium are used and secondary metabolites build up division can halt
This is sometimes because metabolites can be toxic
(cells cm-³)(logarithmic scale)
Number of micro-organisms
time
Stationary phase

25. Cells dying exceed new cells being produced
Population may be totally wiped out or a few resistant spores remain
(cells cm-³)(logarithmic scale)
Number of micro-organisms
time
death phase

26. Complete the graph and table in your notes
(cells cm-³)(logarithmic scale)
Number of micro-organisms
time
Lag phase
log/exponential phase
Stationary phase
death phase
Complete the graph and table in your notes

27. Quick Questions: On your whiteboards
In which phase does bacterial cell division equal bacterial
death?
In which phase are the bacteria metabolically active but not
dividing?
In which phase are the bacteria doubling at a constant rate?
In which phase does bacterial cell death exceed cell division?

28. Controlling metabolism
Some micro-organisms exhibit primary and secondary metabolism 28

29. Primary metabolism
Primary metabolism is during active growth (lag and exponential phases)
Substrates are broken down to obtain energy and primary metabolites
e.g. Amino acids for growth and to increase biomass 29

30. Secondary metabolism
Secondary metabolism occurs at the end of the exponential phase and during the stationary phase
Secondary metabolites are produced though are not used for growth
e.g. antibiotics 30

31. Word Splat! Cyclic fluctuation Migration Daily Torpor Extremophile
Predictive
Transmitter
Dormancy
Hibernation
Innate
Learned
Aestivation
Consequential

32. Manipulating metabolism
Learning Intentions
What effects do metabolic precursors, inducers or inhibitors have on products of microorganisms?
What is the effect of secondary metabolism on growth of microorganisms?

33. Secondary metabolism
Secondary metabolism occurs at the end of the exponential phase and during the stationary phase 33

34. Antibiotics
Secondary metabolites do not have a direct relationship with the growth of a cell but are of ecological advantage
e.g. Antibiotics inhibit the growth of bacteria allowing the fungi to survive and thrive.
They often have economic value 34

35. Micro-organism
Secondary metabolite
Use
Use for organism
Use for humans
Blakeslea trispora
Carotenoids
Yellow pigment
Photosynthetic pigment
Dietary supplement
Fusarium moniliforme
Gibberellins
Plant hormone
Promotes growth
Can be applied to other plants
Penicillium chrysogenum
Penicillin
Antibiotic
Reduces competition from bacterial species
Treat bacterial diseases
Note down two secondary metabolites and their uses. (the ones you’re most likely to remember)

36. Industrial manipulation
Micro-organisms are usually used to overproduce one specific metabolite
This is not always the final product but we manipulate their metabolism to gain large quantities of our desired product 36

37. Manipulating metabolism
Metabolism in micro-organisms can be manipulated in a similar manner to more complex organisms. Using;
Precursors – metabolites in the metabolic pathway that lead to the production of the desired protein
Inducers – Molecules that switch on genes to produce certain enzymes
Inhibitors – switch off the activity of enzymes 37

38. If you wish a cell to produce a large quantity of metabolite C;
What precursors would you add?
What inducer would you add?
What inhibitors would you add?

39. Tasks
Complete the TYK on page 200 of the textbook